VCSU Macro-Invertabrate Lab

Phylum Nematomorpha - The Horsehair Worms

Members of Nematomorpha are known as horsehair worms or Gordian worms. Their resemblance to horsehairs led to the unscientific belief that if a horse hair fell into water it automatically became a horsehair worm. These worms live in ponds, lakes, streams, and even puddles. They are often found wound around other objects or each other. Adults are slow and live only a short time.

General Life cycle - The life cycles of nematomorphs are uncertain and appear to vary between species. Horsehair worms begin as eggs laid either singly or in long threads which may include a million or more eggs. After a period of weeks to months they hatch into microscopic larvae. These larvae may form cysts on plants or be eaten directly by terrestrial or aquatic insects. After some time the larvae mature inside their host into adults. Other horsehair worms may require a second host to mature. When the host enters the water again, the mature horsehair worm bursts out of the body and lives freely in the water. Adults do not feed. Males die after copulation and females die after laying their eggs.

Identification - Horsehair worms are long (10-70 cm), thin (0.3 2.5 mm), unsegmented worms. Their entire body has the same diameter except at the extreme ends where it may taper slightly.

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